Gear pump



Patented Jan. 6, 1953 GEAR PUMP Borrar'. nyin; cleveland, ohio, assigner-,w1 Borg:-

Warner Corporation, Chicago, IllL, a corporation of Illinois' Application October 8, 1949, Serial No. 1Z0-,349

This invention' relates; to a gear pumpL and more..'-Iatrticularly' to' a gear pump .ofl the type, em'- ploying pressurel loaded bushings, such gear pumps? sometimes being referred to as pressure loaded-pumps. v

As is Well known'.v inl a pressure4 loadedv gear pumpof the type including one set of axially movable', pressure loadable bushings, a part of the outputpressure' is applied to the rear or motive. surfaces ofA the axially adjustable bushings to urge these bushings intosealing relation with their associated gears. As disclosed in U. S. Patent No. 2,420,622' to Roth et al., by carefully selecting. the relativev areas of the forward surfacesrof thebushings and ofthe motive surfaces; of the bushings, it is possible to control within very closelimitsthe actual sealing; pressureprovided; Gear pumps so constructedv are capable of delivering fluid at extremely high pressures with considerable volume.

When such'pumps are operated atV high pressures.- the bearing loads also become very high, resulting in Wear. Because of the self-adjustingcharacteristics ofv pressure loaded bushings,` a considerableamount of wear may be tolerated; provided that` such wear is uniform. However, it has been foundV that in a gear pump the jour-v nal loads on the drivingy gear are substantiallyless than the journal loads-on the driven gear. This dierential in journal load is due primarily to the fact that the driving loads. deduct-from the-driving gearbearingv loads andladd', by alike amount, to the' drivenY gear bearing loads. It has-been foundinpractce that the difference may amount to there being-v asr much.` as 40% less loadonf the driving' gear than onv the driven gear. Thisunevenl or ui'ibalanced` condition results in greatly increased'- weer and reduces the useful life of the pump; The bushingsltendto move relatively toeachfotliei andthe gear'teeth, instead of mesh-A ing evenly, will tend to eut-into each other as the wear on one bushing progressesn at a more rapid rate than onl the other bushing.

An; object ofk the present invention is. torerovide anew andnnproved pressure-V lo'adecl. type' intc'rme'shing geen pump wherein the journal loads betweenv the driving' and the'l driven 'gears are` made. substantially equal. y y l In accordance with one embodiment. of this invention.. eachof the pressurer responsive; bushings of apressure loaded type intermeshing gear pump may have" formed in the gear side-'jface engagingusurfa'ce thereof an arcuate balancing grooves disposed coaxial-1v of; the. bushing-and adjacent the gear teeth., Gineendfofeae'h groove- 3 Claims. (Cl. 10S-126) communicatesl with. the; discharge: side4 of.'A ther pump. The grooves are of, unequal length the groove. inthey bushing'` associated-withv the driven gear being. substantially longer than the groove formedl inthe forward. surface of. the bushing associated with the driving gear.. At the same time. theinlet portA is offset withrespect to the center line of the pumpk so that the groevey as,- sociated. with the' driven gear bushing; may be conveniently extended Without establishing corn.- munication through the groove. and the gear teethv with the'inlet side ofi the, pump.

Other objects and advantages of the. present invention willbe apparent from the followingv detailed description taken in conjunction with the drawings wherein:

Fig. 1 is. a fragmentary. axial, sectional view of.' a pressureloadedtype intermeshing gear pump constructed in accordance with one embodiment of this invention; and` Y Fig.k 2 is a.vertical, sectional view taken substantially alongthe-line 2-2 of Fig. 1 and showing tofadvantage the` arrangement of the balancing grooves and the ports of this pump.

ReferringA to the drawingsis the numeral 5y denotes a suitably chambered gear pump housing in which are rotatably mounted a driven gear 6 and a driving. gear 'l intermeshing therewith. Driven. gear 6- is supported on a shaft 8 journalled through an` axially displaceable,l flanged bushing 9. disposed on the left side of driven gear 6 and a fixed, flanged bushing I0 disposed on the rigl'itside.v of. gear 6, as. viewed in Fig.k 1. The gear. 6 and; associated bushings 9 and I0 are arrangedV in a first bore I2 formed in the pump housing: 5,. sufficient clearance being. provided. between the left end of bushing 9 andthe end; wall. of the housing. to permit4 axial movement. of the bushing 9. Similarly,y the driving gear l has disposedY on the. left side thereof a pressure responsive;` axially movable', flanged bushing I3" and a xed,l anged bushing I4. is disposed on the right side thereof. Driving shaft I5 on whielrgear l isy moulded is journalledl in the bushings; I3' andv I4 andy mayv beV suitably secured. to any driving means; (not shown). The gear'l" and bushings I' and yIII arev located in a second here formed in housing 5: adjacent and parallel tot bore I2` Sufficient clearance is provided between thev left end ofbushing I3 and the adjacent wall of the housing 5 -to permit axial displacement of the bushing.

. As bestshown' in Fig 2, housing 5. has' iormed the' left side thereof an inlet port |16' and;` on

se the righe side thereof m esi-iet por-c. n; enea the bushings on the opposite side from the passage I8 to prevent recirculation of pressure fluid back to the inlet side of the gear teeth. Previously, it has been the practice to provide al closure plug (not shown), but this is not generally necessary.

In accordance with usual pressure loaded pump practice, the radially inner, terminal portions of the forward or gear engaging surfaces of the axially movable bushings have formed therein relief recesses 20 of annular configuration, these relief recesses being placed in communication with the low pressure or inlet side of the pump through axially extending channels or grooves 2I formed through the bushings. These recesses control the effective pressure area of the flanged bushing surfaces or forward surfaces and, hence,

the axial forces tending to produce axial movement of the bushings away from the gear side faces. The areas of the pressure responsive motive surfaces are selected so that the forces tending to establish a seal slightly exceed the forces tending to separate the bushings from their `associated gear side surfaces.

From the foregoing, it will be readily evident that while the loading pressure will be substantially uniformly distributed over the motive surfaces of the pressure responsive bushings 9 and I3, there will be a very definite pressure gradient between the portions of the bushings adjacent the inlet I5 and the portions of the bushings adjacent the outlet I'I, which latter portions will, of course, be subjected to the higher or discharge pressures. A partial answer to lthis problem is to provide balancing grooves such as the arcuate semiannular grooves 22 and 23 formed in the forward or gear side face engaging surfaces of the axially movable bushings 9 and I3, respectively. The right ends of these grooves, as viewed in Fig. 2, communicate with the discharge side of the pump, and the grooves are spaced radially outwardly of the gear tooth pockets sc as to communicate pressure thereto. Because the grooves extend toward the inlet side of the pump, although not suflciently to actually communicate therewith, to the extent that the grooves extend, discharge pressure is communicated to a larger 'area of the g'ear side fac'eengaging surfaces of the bushings, and the actual pressure per square inch across the gearside faces will tend to be equivalent to that acting on the .motive surfaces ofthe bushings.

It will be apparent that to a' large extent it is possible, by employing balancing grooves, to balance out on each gear the journal or bearing loads, since any pressure applied on the inletside of the gear will tend to reduce the bearing loads. However, as pointed out hereinbefore, it has been found in practice that the journal load on the driving gear is approximately 40% less than the journal load on the driven gear, and that rather than attempt to reduce the over-all journal load A.to the4 maximum extent feasible, it is more desir,-

ableto reduce the-journal load'on the' driven gear so that it may be made substantially equal to the journal load on the driving gear. Thus, it has been found desirable to make the balancing grooves of unequal length and to form the longer balancing groove in the bushing associated with the driven gear. In this manner, the journal load on the driven gear may be reduced more than the journal load on the drivinggear and thereby the two' journal loads made approximately equal.

In order to permit extending the balancing groove associated with the driven gear to the maximum feasible extent, the inlet port I6 is offset with respect tothe center line of the gear pump so that while a smaller area ofthe driven 'gear 6 is exposed to the inlet port, a larger area of the gear 1 is exposed. By locating the walls of the inlet port so that the teeth of both gears coincide therewith at the same time, pulsations at the inlet may be reduced in frequency with a definite improvement in the inlet characteristics of the pump,particularly where 'tl'ie pump is associated with a booster pump. This desirable location of the inlet port may be made in oisetting the inlet port to permit extending the groove associated with the driven gear,'in accordance with the present invention. I f

It will be understood, of course, Vthat neither groove must be so long that at the time any gear tooth pocket is exposed to the inlet port, the end of the groove is also in communicationwith that tooth pocket. To do so would cause an undesirable loss of pressure.

Because of the disparity in length of the balancing grooves and the offset arrangement of the inlet port, it will be apparent that more gear tooth pockets on the inlet side of the driven gear will be exposed to discharge pressure than on the inlet side of the driving gear. Discharge pressure applied on the inlet side of the gear will, of course, tend t0 reduce the bearing loads and since a greater area of the driven gear is exposed to discharge pressure on the inlet side thereof, the reduction in bearing load is greater on the driven gear than it is on the driving gear. It will thus be evident that by properly selecting the relative lengths of the balancing grooves, not only can an over-all reduction in bearing load be achieved, but also the bearing loads of the individual gears may be largely equalized.

Where herein the various parts of this invention have been referred to as being located in a right or a left position, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative positions of the partsas shown in the accompanying drawings.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modicationsmay be made therein without departing from the spirit or scope of the invention.

What is claimed is:

l. In an intermeshing gear pump, Va housing having an inlet port and a discharge port formed therein, a pair of intermeshing pumping gears journalled in said housing and arranged to force liquid from said inlet out "of said housing through said outlet, a pair of bushings associated with said gears and having surfaces adapted to engage the adjacent gear side faces in substantially sealing relation, and means for communicating discharge pressure generated by said gears to gear tooth pockets lying adjacent the inlet port of said pump during the operation thereof, said means comprising a groove formed in the gear side face engaging surface of each of said bushings and communicating at one end With the discharge port of said pump and at the other end with gear tooth pockets of the associated gear adjacent the inlet port of the pump, said grooves being of unequal length and the groove associated With the driven gear of said pump communicating at any instant with more gear tooth pockets than the groove associated with the driving gear whereby a greater number of gear tooth pockets of the driven gear are exposed to discharge pressure than of the driving gear.

2. In an intermeshing gear pump, a housing having an inlet port and a discharge port formed therein, a pair of intermeshing pumping gears journalled in said housing and arranged to force liquid from said inletrout of said housing through said outlet, a pair of bushings associated With said gears and having surfaces adapted to engage the adjacent gear side faces in substantially sealing relation, and means for communicating discharge pressure generated by said gears to gear tooth pockets lying adjacent the inlet port of said pump during the operation thereof, said means comprising a groove formed in the gear side face engaging surface of each of said bushings and communicating at one end With the discharge port of said pump and at the other end with gear tooth pockets of the associated gear adjacent the inlet port of the pump, said grooves being of unequal length and the groove associated with the driven gear of said pump communicating at any instant With more gear tooth pockets than the groove associated with the driving gear whereby a greater number of gear tooth pockets of the driven gear are exposed to discharge pressure than of the driving gear, said inlet port being offset with respect to a reference plane extending along the common tangent to the pitch circles and parallel to the axes of rotation of said gears.

3. In an intermeshing gear pump, a housing having an inlet port and a discharge port formed therein, a pair of intermeshing pumping gears journalled in said housing and arranged to force liquid from said inlet out of said housing through said outlet, a pair of bushings associated With said gears and having surfaces adapted to engage the adjacent gear side faces in substantially sealing relation, and means for communicating discharge pressure generated by Said gears to gear tooth pockets lying adjacent the inlet port of said pump during the operation thereof, said means comprising a groove formed in the gear side face engaging surface' of each of said bushings and communicating at one end with the discharge port of said pump and at the other end with gear tooth pockets of the associated gear adjacent the inlet port of the pump, said pump having a reference plane passing through the common tangent of the pitch circles of both gears and parallel to the axes of rotation of said gears, said grooves being of unequal length and the groove ends adjacent the outlet of said pump being exposed to outlet pressure during the operation of the pump, the groove associated with the driven gear having its end adjacent the inlet of said pump closer to said plane than the corresponding groove end of the groove associated With the driving gear.

BORIS P. ILYIN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 917,466 Lees Apr 6, 1909 1,007,742 Smith Nov. 7, 1911 1,937,367 Vickers Nov. 28, 1933 1,978,480 Svenson Oct. 30, 1934 2,212,994 Vrolix Aug. 27, 1940 2,221,412 Rose Nov. 12, 1940 2,233,709 Osborne Mar. 4, 1941 2,281,767 Heckert May 5, 1942 2,293,126 Fersing Aug. 18, 1942 2,338,065 Herman Dec. 28, 1943 2,345,975 Ungar et al Apr. 4, 1944 2,349,022 Roth May 16, 1944 2,405,061 Shaw July 30 1946l 2,420,622 Ernst May 13, 1947 2,433,360 Haight Dec. 30, 1947 2,544,144 Ellis Mar. 6, 1951 FOREIGN PATENTS Number Country Date 300,832 Germany Dec. 13, 1949 325,849 Germany Sept. 21, 1920 478,268 Great Britain Jan. 17, 1938 

